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Aptitude - Logarithm

Exercise : Logarithm - General Questions
11.
If log 2 = 0.30103, the number of digits in 264 is:
18
19
20
21
Answer: Option
Explanation:

log (264) = 64 x log 2
= (64 x 0.30103)
= 19.26592

Its characteristic is 19.

Hence, then number of digits in 264 is 20.

12.
If logx 9 = - 1 , then x is equal to:
16 2
- 3
4
3
4
81
256
256
81
Answer: Option
Explanation:

logx 9 = - 1
16 2

x-1/2 = 9
16

1 = 9
x 16

x = 16
9

x = 16 2
9

x = 256
81

13.
If ax = by, then:
log a = x
b y
log a = x
log b y
log a = y
log b x
None of these
Answer: Option
Explanation:

ax = by

log ax = log by

x log a = y log b

log a = y .
log b x

14.
If logx y = 100 and log2 x = 10, then the value of y is:
210
2100
21000
210000
Answer: Option
Explanation:

log 2 x = 10         x = 210.

logx y = 100

y = x100

y = (210)100     [put value of x]

y = 21000.

15.
The value of log2 16 is:
1
8
4
8
16
Answer: Option
Explanation:

Let log2 16 = n.

Then, 2n = 16 = 24         n = 4.

log2 16 = 4.

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